An effective road profile control (ERPC) process for use with spindle-coupled road simulators, as disclosed in U.S. Pat. No. 5,610,330, assigned to the assignee of the present invention and incorporated herein by reference, provides a method by which measured vehicle data from a first vehicle can be used to develop a valid simulation test for subsequent vehicles. The process uses an analytical tire model to predict a tire profile which is consistent with vehicle dynamics, including spindle force and acceleration, from the first vehicle. In developing the simulation test on subsequent vehicles, a second tire model is used as a parametric observer in the system tracking-control process, generating a test where the predicted tire profile of the measurement and test vehicles are the same.
This approach to simulation test control assumes that the longitudinal, lateral, and vertical tire profile displacements are independent of the vehicle and only a function of the road surface. This assumption is normally valid for most regions of a measured road surface, since the tire profile is normally being directly loaded by the road, and the tire profile and the road profile are coincidental. For some road events, however, the tire profile can be independent of the road profile. These events may include tire hop, where the tire loses vertical contact with the road surface. In this situation, the tire is momentarily free of the influence of the road profile, but typically quickly reengages with the road.
Another potential problem with the assumption that the tire profile matches the road profile occurs in the longitudinal control axis. A free rolling tire on a smooth surface, such as between pot holes or bumps, can have longitudinal tire profile motion which is a function of only the vehicle. Transient response oscillations of the suspension following an impact event are dictated by the dynamics of the suspension alone, which may be dependent on suspension mass, stiffness, damping and other parameters. Under these conditions, forcing a calculated longitudinal tire profile to match a previous vehicle's tire profile may not be accurate.
While the above recited patent represents a significant advance in the art, further advances are needed to overcome the above described problems.